The invention relates more particularly to an installation for manufacturing containers from a preform made of thermoplastic material, comprising at least one protection chamber intended to isolate an internal volume of the installation from the ambient air contained in industrial premises where the installation is located and comprising, arranged in said internal volume, at least:                a device for decontaminating the preforms by the application of at least one sterilizing agent,        a thermal conditioning unit for the preforms consisting of an oven comprising heating means associated with an air cooling device which comprises means for filtering the ambient air and ventilation means specifically for ensuring a cooling of at least a part of the preforms,        a unit for transforming the preforms into containers,and comprising an extraction system suitable for extracting, from the internal volume of the chamber, air charged with sterilizing agent to evacuate it into the atmosphere, outside the industrial premises, via at least one exhaust duct.        
Installations of this type are known, for manufacturing containers, in particular bottles, flasks, etc. from preforms or blanks previously obtained by injection of thermoplastic material, in particular of PET (polyethylene terephthalate).
As an example, the document EP-2.191.953 describes in particular a thermal conditioning oven for a container manufacturing installation.
To produce sterile or aseptic containers, the installation generally includes a decontamination device or module suitable for treating the preforms by means of a sterilizing agent.
In the field of container manufacturing, the sterilizing agents used are, for example, hydrogen peroxide (H2O2), peracetic acid or any other product recognized for its aseptic, in particular bactericidal, properties.
According to the teachings of the document WO-2006/136498 or WO-2006/136499, the decontamination device is, for example, suitable for spraying toward the preforms a flow of sterilizing vapor, advantageously a jet of dry vapor, containing a vaporized sterilizing agent intended to be deposited by condensation in the form of a uniform film of sterilizing agent mist, at least on the internal wall of the preforms to be sterilized.
The preforms are then introduced into the oven of the thermal conditioning unit where the heating means, for example infrared radiation lamps, then provoke the thermal activation and the evaporation of the sterilizing agent previously deposited by condensation.
When the installation comprises such decontamination devices, it is necessary to prevent the diffusion of sterilizing agent in the ambient air around the installation, in particular when the latter is in the gaseous state.
In fact, the vapors of sterilizing agent such as hydrogen peroxide are, on the one hand, poisonous to human health and, on the other hand, corrosive to the metal materials used in the installation, in particular in the oven or the transformation unit.
Consequently, it is important to ensure both the protection of the operators working on the installation and that of the installation itself in order to avoid the degradations that can be attributed to the corrosive effects of the vapors of sterilizing agent.
This is one of the reasons why a container manufacturing installation generally includes a protection chamber ensuring the individual containment of all the manufacturing means and an associated extraction system for evacuating the air charged with sterilizing agent.
In some of the Applicant's installations, the extraction system comprises at least first extraction means associated with the decontamination device that are intended to evacuate into the atmosphere the air contained in a sterilization chamber of the device, that is to say evacuate the air charged with sterilizing agent outside the building in industrial premises in which the installation is located.
The air contained in the sterilization chamber is the most charged with sterilizing agent, notably present in this air in the gaseous state when it is applied to the preforms according to the abovementioned condensation deposition technique.
However, such a method for applying the sterilizing agent advantageously makes it possible to considerably reduce the quantity of agent used while obtaining an improved effectiveness.
Preferably, the extraction system of the installation comprises second extraction means which, associated with the oven, are intended to evacuate into the atmosphere, therefore outside the industrial premises, the air contained in the internal volume of the oven delimited by a part of the chamber of the installation.
By virtue of such second means of the extraction system, on the one hand the calories (hot air) and, on the other hand, the sterilizing agent present in a smaller proportion in the gaseous state in this air, are evacuated jointly out of the oven.
It will be recalled that the presence of sterilizing agent in the cooling air extracted from the oven results from the evaporation by heating in the oven of the sterilizing agent, such as that of the uniform film of sterilizing agent deposited by condensation in the sterilization chamber of the decontamination device.
Advantageously, in the extraction system of an installation, the first extraction means associated with the decontamination device comprise a suction duct, the output of which is connected to the exhaust duct that the second extraction means associated with the oven comprise.
Thus, by virtue of the chamber and of the first and second means of the extraction system, the extraction system evacuates to the atmosphere via the exhaust duct, on the one hand, the heat produced by the heating means of the oven with the constantly renewed cooling air introduced by the ventilation means and, on the other hand, the sterilizing agent coming from two sources, namely, respectively, most from the sterilization chamber of the decontamination device and the remainder from the oven.
Ultimately, the concentration of sterilizing agent present in the air discharged by the extraction system conforms to the environmental requirements.
In practice, the concentration of sterilizing agent is primarily high in the sterilization chamber of the decontamination device, said concentration of sterilizing agent being automatically reduced by dilution in the cooling air extracted with a very much higher flow rate by the second means of the extraction system, by virtue of which the concentration of sterilizing agent in the air finally discharged into the atmosphere does not exceed the authorized limit values.
The flow rates of air extracted from the installation by such a system can, for example, reach values of the order of 20 000 to 30 000 m3 of air per hour depending on the type of oven and the dilution phenomenon is directly linked to the significant air consumption of the oven, since that of the decontamination device does not contribute more than 1000 m3 per hour to it.
In such an installation, the air is thus systematically evacuated into the atmosphere via an exhaust duct of the extraction system and this is done to evacuate both the heat and the residues of sterilizing agent.
However, the Applicant has been able to establish that the significance of the air flow rates attributable both to the cooling device and to the extraction system of the installation indirectly had negative consequences on the container manufacturing quality.
In practice, the air evacuated into the atmosphere is automatically replaced in the industrial premises by being mainly renewed by air originating from outside the building housing the industrial premises. Now, the qualities of this atmospheric air, introduced into the industrial premises from outside to compensate the significant quantity of air evacuated by the extraction system, are not controlled.
In particular, the temperature of the air, its relative humidity and even the undesirable presence of dust like bacteria are not controlled and are all parameters directly influencing the quality of manufacture.
In addition, such parameters fluctuate according to the geographic location of the building containing the installation, or even—for one and the same location—according to the season which is likely to modify some of these qualitative parameters such as the temperature of the air (even over one and the same day).
However, for the person skilled in the art, the evacuation of the air by such an extraction system appears essential, in particular because the air contains sterilizing agent.
Furthermore, the person skilled in the art also considers the fact that the extraction system makes it possible to simultaneously evacuate the calories deriving from the heating provided in the oven, thus limiting the transfer of heat from the oven to the ambient air.
To check the quality of the ambient air in the industrial premises, it is possible to resort to a transformation of the industrial premises to make it a “clean room”, that is to say a sealed enclosure designed to eliminate dust and microorganisms as far as possible, to obtain ultra-clean manufacturing industrial conditions in the industrial premises.
However, it will easily be understood that, while such a transformation is always possible, the associated costs, both to transform the industrial premises and subsequently to operate the installation, are very high and prohibitive.
It is known from the document EP-1.941.913 to evacuate the vaporized sterilizing agent used to sterilize the preforms, and from the document FR-2.774.912 to recycle the sterilizing agent vapors.
Also known from the document JP-2008.207434 is a conditioned air device recycling air extracted from an area in which an oven is arranged, which air does not however contain any sterilizing agent in the absence of decontamination.